Considerations about the relationship of inhibitory concentrations and the pharmacologic and toxic properties of antimicrobial agents.

Too little attention has been given to the correlation of antimicrobial susceptibility tests and the pharmacokinetics of antimicrobial agents. Ability to perform and provide reproducible, rapid, minimal inhibitory concentration data, combined with the knowledge of serum levels, can be used to yield inhibitory quotients which will improve the chemotherapy of serious infections. Antimicrobial susceptibilities have to be provided rapidly for the life-threatening infections that occur in certain clinical settings. Antimicrobial susceptibilities also must be provided in a manner that demonstrates that one may not be able to achieve therapeutic concentrations with certain drugs. We have reached an era in which knowledge of an organism being susceptible or resistant is no longer adequate.